1. Field of the Invention
The present invention relates to a webbing retractor that takes-up and accommodates a webbing belt for restraining the body of a vehicle occupant seated in a seat.
2. Related Art
A locking mechanism, which restricts rotation of a reel shaft (a spool) in a pull-out direction at a time of rapid deceleration of a vehicle, is provided at a webbing retractor which structures a seat belt device of a vehicle, as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 5-246303 for example. A lock gear, which structures the locking mechanism disclosed in JP-A No. 5-246303, is able to rotate coaxially with and relative to the reel shaft. When the reel shaft rotates in the pull-out direction relative to the lock gear, interlockingly with this relative rotation, respective teeth of a main pawl and a back-up pawl engage with internal teeth which are formed at both side walls of a frame, and rotation of the reel shaft in the pull-out direction is restricted.
As one structure for causing relative rotation between the reel shaft and the lock gear, there is an inertial body which is provided at the lock gear. The inertial body is connected to the lock gear by a spring. When the lock gear rotates suddenly in the pull-out direction together with the reel shaft, a delay in rotation with respect to the lock gear arises at the inertial body due to inertia and against the urging force of the spring. Accompanying this relative rotation with respect to the lock gear which is due to the delay in rotation, an anchor claw formed integrally with the inertial body moves outwardly in the rotation radius direction of the lock gear. The anchor claw engages with a ratchet tooth which is an internal tooth formed at the inner peripheral surface of a first cover of the lock gear, and rotation of the inertial body, and accordingly of the lock gear, is stopped. Due to the rotation of the lock gear being stopped in this way, the lock gear rotates relative to the reel shaft which rotates in the pull-out direction.
In such a webbing retractor which operates the locking mechanism from a webbing sensor, high precision and rigidity are required of the respective members in order to match the engagement phase of the anchor claw of the inertial body and the ratchet tooth which is an internal tooth of the lock gear, and the engagement phase of the main pawl and an internal tooth of the frame.